Alarm system



Sept. 14, 1943. T. DlMoND ALARM SYSTEM Filed March 15, 194;

` Patented Sept. 14, 1943 y ALARM SYSTEM ,y Thomas L. Dimond', Rutherford, N. J., assignor to Bell Telephone Laboratories, Incorporated,` New York, N. Y., a corporation of New York Application March '15,.' 19211 senat-No: 383,516

y' 5 Claims.'r 1.'(,Cl. 177-311) This invention relates to fuse alarm systems and more' particularly to improvements in such systems employing so-called alarm fuses which operatare'sponsive to ruptureof "the fusible element, to connect the current vsourceltoa relay which'in operatingY controls any Vdesired arrange* ment of 'signal devicessuch as lampsjbells, or combinations of both. l f

It is a well-understood practice. telephone exchangesA to connect the main or central cnice battery, throughfa'mainiuse, to a pluralityof branch 'circuits Ywhich "supply direct current' to small switching circuit groups, for example, small groups of automaticv switches ,and their associated equipment and circuits; y These small groups of switches and associated circuitsare yusually mounted in horizontal" rows, one abovehanother, on iron frames' which rows arey sometimescalled shelves. Low frequencyalte'rnatingringing curff l rent is also supplied to Aeachshelf off switches. Irlr order that `a short circuit ground Ain the switching circuits Aoffone ofthe above-described shelves shall not affect the supplyci current to' other shelves it is the practice to, provide each shelf with so-called alarm fuses of the-,type disclosed inPatent 819,959 toE. B. Craft, issued Aprill'l, 1906, which alarm fusesare connected in series with l: otl' i.the..battery5and ringing cur,-

`rent supplied to the"y shelf equipment.'v f

Itis well understood thatthe ruptureyof the fusible element of these alarm fuse devicescauses the incoming supply. conductor to befconnectecl to ground through a relay, usually common toa number of shelves, thereby causingtherelayto operate which in. turn causes a bell to ringars a trouble signal to the attendant." Due to the fact that both alternating and direct currents are involved in the arrangement above described it is obvious that two commorifalarmrelays are required for apredetermined number of shelves,V

one relay being responsive to alternating current and the other responsive to direct current. p

Further, in order t`o insure prompt llocationof the shelf on which theoperatedwfuse is located the practice is to also 'provide 'lamps on each shelf, one foreach alarm fuse, which lamps are connected in the respective leads to the alarm relay which light as soon as the respective fuse p operates. to serve as a visual indication of the shelf on which the trouble has occurred. It `will therefore be noted that a minimum of twocoml the fusiblevelerne'nts, s i'uclhgas oi-. k 5,Vcloses`a I lormally open contact, such as Il yor l0, between mon relays plus two lamps per shelfare required for each exchange and as the size of the ex` change increases the number of alarm relays Will also increase, it being understood that in pracnand lilV supply a plurality ments''(notshown);v

.tice at least onel direct current relay and one alternating. current -relay will be required `for feach line of switch frames. n I

Y Anobjectoffthe present inventionistoreduce the number! ofecommonl alarm'relaysfand the numberfof .shelf flam'ps'required for vtelephone exchangez Afuseffala'rm systems of the character Tdescribed.,v

The improved' arrangementtaccording to the present invention, vvvherebythe foregoing object is attained, will be understood from the following description and accompanying drawing; which shows a source .oftaltern'a'ting current and a source of 'directfcurrent,each source supplying ay respectivefload circuit, an alarm fuse individual to each load' circuit, r.an alarm relay directly controlledi bythe operation ofA ya rst one of A.said alarm .fuses and means comprising a third or additonal alarm. fuseiso connected andarranged .that ruptureof the second fuse will cause rupture andoperaton ofthethird fuse `to connect the source of currentassociated with the yfirst fuse to the alarm relay independent of the rst fuse. f Referringto the drawing',a' source of alter- `natirgringingcurrent Land avsource of` direct A'current'v Bare shown. connectedto .respective load circuits. 2. and .1 to .supply ringing land direct currenttocircuitsof a so-calledshelf of automatic switches `(not shown), which .load l.circvzuits include respectivel alarm fuses 4 and 6'.

The circuits shown'to theright and above'lthe -brokenline a-a' are individual to one switch shelf'and itfwill be understood that sources vI of other shelf equip- Y Below the broken linea-.afand comm-on to a plurality of other shelf equipments, is a direct current relay 'v8 adapted to control an auxiliary circuit including anfaudible signaIdeVice, such jas abell 5. Y *Y Alamiuses 4 Svmaybe of the type de- -gscribedlin the before.*Irieiilsioi'ieil Craft Patent 817,959. and areso constructedand arrangedthat when connected betweenacurrent Asource and a load circuit,; in the manner shown, rupture of the current-supply source'and a third terminal, such `las l2 or I8.` In theA present arrangement alarmv fuse 6 is shown connected as usual, in the battery (direct current) load circuit l,

xwhereby ruptureof its fuse 5, 'due to a ground I9 ontherload circuit 1, permitsv closure of contacts I tojclose a circuit from the battery B to ground in series with relay 8, which, in turn, may con- 'the associated device tociose.

'are inp'aralle-l wthccntacts I0 lcizievijceii,'relay 8 n,Will be operated from battery B asin-tire case nected that-'the consequent rupture of fuse I5y by closure of this circuit permits contacts IB to close thereby completing an Operating Circ for Tela-Y 3, from battery B, independent of ccntacts I of fuse alarm device 6.

Operation of the alarm-,system of the invention is obvious from the abovev description., i.; e,"

if an excessive load is placed 0n the' battery ica-d closure of contacts I0 of device E 'to cause opi eration of relay 8 and audible signal 9. e Onthe.

other hand, if an excessive 'load is placed on 'the zingingvolta'ge source I', as Tor 'example' *oy a low resistance ground connectionj'IS, fuse 3 will be ruptured thus 'permitting contacts-II to ciose a low resistance ycircurt iromthe .grounded ringing source I 'to the gromrded battery B in `series with fuse I5 o f the 'aux'iarvdev'rce 1% which causes immediate rupture cf the l'fuse 5. When fuse I5 ruptures it permits contacts IB of A's these contacts f As va visual `indicati-on'di a ruptured fuse associate-d With eitherfloa'd a damp 2% is con"- Anectefd in the Vconduct-m' j2| 'common to alarm tenninalsn and I8 lof prees Ii 'and 'B, 'which lan'ip'ligh'ts Whenever 'contact HS "or I8 closev to 'connect battery *By yto thecommon reiay "3 it being understood `that asimilar lamp 'is conin `t'l'i'e lsame manner :and associated lamps one 'for 'each 4l'ofazd circuit as inthe 'case- 'of :prior arrangements.'

twili also be understood .that the I:operat'ic-iu c fthearrangement shown will be the same the alternating source I and battery 'jB arexi'rrterchanged with respect to load circuits f2 and I and -`the relay '8 iscorrstructedto 'respond to alternating instead of direct current.

Wh'a'tis'claimcdsl; i Y j L i. In na fuse `alarm system, a first source ,of

current, au alarm device. adapted to .operate in 'response to 'connecticnff Isaidiirst source thereto, a secondy 'source 'of 'current 'having a diiferent characteristic from 'inst source, a'lca'dcir- 'cuit 'connectedto said second soluce, a matin alarm l'fuse and anauxiliary ail'armfuseysaiu main i ffuse being included in vsaid ioa'd 'circuit andV adapted when ruptured to disconnect said load circuit therefrom and connect said second source in series with said auxiliary fuse to said first source, said auxiliary fuse being arranged to con- 5 nect said rst source to, said alarm device when ruptured.

2. In an alarm system, rst and second sources of diierent characteristic current supply, individualload circuits connected to each source, an .individual yalarm fuse in Vseries with each load circuit, a signal device adapted to be operated by said iirst source responsive to operation of the associated fuse device, and means including an auxiliary alarm fuse device adapted to be operexcedan-d to connect said rst source to the signal Lxmlievil iespcnsiveffto operation of said second l I"misedevice. circuit 1, fuse 5 Will rupture thereby ,permitting i.,

3. In an alarm system,'a rst source of curren'thav'ing a grounded terminal, a grounded .20 alarm device arranged to operate in response to the connection of said first source thereto, a 'secondV grounded source Aof currentV having a dii- `ferent' characteristic .from saidA 'iirst source, a r4'l'oa'cl circuit connected to said second source, main and auxiliary alarm 'luse devices each including a 'fuse element, saijd 'main device being arranged 'to disconnect 'said second source from the 'load circuit 'and connect said second 'sourcefto said iirstsorce in series With'sa'id auxiliary device responsive to rupturer of .said main device 'fuse feiem'ent, said auxiliary device being so arranged that rupture of its respective fuse element fol- *lowing rupture 'of the m'aindevic'e fuse Will conneet said first source to, said alarm device.

4.'111 'a fuse alarxnsystem for telephone exchanges, a sourcey of 'direct current having one pole grounded, 'a direct cmrentre'lay'having one rterminal connected to 5a. g'ounded source Iof alternating rcurr-enig, at loadjcircuit connected thereto, Aa; first alarm 'fuse in 'said load circuit having anular-m terminal and adapted when ruptured in response; to apredetermined current flowing thereinto"'connect 'said' 'alternating source "to thealafrm 'termina-l thereof, an 'auxilr ziaiyv aiann 'fuse also having ,an alarm terminal, fa connect-ion between said rst 'alarm terminal vand said ldirect 'current source including `said .auxiliary fuse, and a connection between said auxilf iary alarm terminal 'and saidIeiay, said auxiliary fuse being-connected between said first alarm terminal and said direct 'current' source in such ay'direc'tion that -when ruptured 'said direct current source will be'connected lto the auxiliary alarm termina'l. i

`'incMas L. DrMoND.

5.'Tn a-n alarm system, a first source 'oi 'cur- I 

